w-form

Implement a form in the current Next app. Follow next-v16 and shadcn-v3. If the app already mutates through an API client (Fastify + TanStack Query), do not introduce Server Actions, useFormStatus, or useOptimistic for those flows.

1. Inspect how neighboring forms submit. Reuse that path.
2. Share one Zod schema for client UX and server validation.
3. Wire accessible labels, errors, pending, and empty/error/success states with existing UI primitives.
4. Run lint and exercise submit, validation failure, and keyboard path.
5. Docs: /w-docs if behavior or commands changed.